PROPYLENE GLYCOL ALGINATE
First draft prepared by
Dr G.J.A. Speijers and Mrs M.E. van Apeldoorn
National Institute of Public Health and Environmental Protection
Laboratory for Toxicology
Bilthoven, The Netherlands
1. EXPLANATION
Alginates are polyuronic acids which are major components of
the cell walls of brown seaweed. Brown seaweeds have been used in
food and feed for centuries but it is only since 1929 that alginates
have been manufactured on an industrial scale. Alginates have
valuable rheological properties which can be varied to a great
extent by varying the degree of polymerisation of the polysaccharide
or by changing the ionic environment. Thus alginates can provide
solutions having a range of viscosities or gels of varying
rigidities which may be used as texture modifiers in a wide range of
food and industrial applications (Martin, 1986).
Propylene glycol alginate is a reaction product of propylene
oxide and alginic acid (Steiner & McNeely, 1951). This substance
was evaluated at the thirteenth, fifteenth, and seventeenth meetings
of the Committee (Annex 1, references 19, 26, and 32). At the
seventeenth meeting an ADI for propylene glycol alginate of 0-25
mg/kg bw was allocated, based on a NOEL of 2 500 mg/kg bw/day in a
long-term toxicity study in rats. At that meeting the Committee
concluded that only the propylene glycol moiety is absorbed and
metabolized, and that the alginate moiety is excreted unchanged in
the faeces of rats and mice. Accordingly, the Committee decided
that the contribution of propylene glycol alginate to total dietary
propylene glycol intake from all sources should be included in the
ADI for propylene glycol, which was allocated an ADI of 0-25 mg/kg
bw (Annex 1, reference 32).
Alginic acid and its ammonium, calcium, potassium, and sodium
salts were evaluated by the Committee at its thirty-ninth meeting
(Annex 1, reference 101) when a group ADI "not specified" was
allocated.
At its present meeting, the Committee evaluated new data from a
30-day study in rats, genotoxicity assays, a teratogenicity study in
rabbits and a study in human volunteers. The previously published
monographs have been expanded and are reproduced in their entirety
below.
2. BIOLOGICAL DATA
2.1 Biochemical aspects
2.1.1 Absorption, distribution and excretion.
In vitro hydrolysis studies with propylene glycol alginate in
simulated gastric juice and simulated intestinal juice showed no
hydrolysis in simulated gastric juice, while intestinal juice
hydrolyzed 25% in 4 hours, 65% in 12 hours and 80% in 24 hours
(McNeely & Shepherd, 1966).
Five grams of propylene glycol alginate/kg bw (as a 10% aqueous
solution), labeled with 14C in the alginate moiety, or 1 g of
propylene glycol alginate/kg bw (as a 5% aqueous solution), labeled
with 14C in the propylene glycol moiety, was administered as a
single dose to mice (8/group) by gavage. Absorption, distribution
and excretion of radioactivity were followed from 1 hour to 5 days
after administration by whole body autoradiography.
Some, but not all, of the label (labeled in the propylene
glycol moiety) in a single dose of 1 g propylene glycol alginate/kg
bw was absorbed. The unabsorbed portion was excreted in the faeces
within 3 days while the absorbed radioactivity was distributed
rapidly over the whole body, was concentrated in the liver and was
completely removed from all tissues in 3-4 days. These findings are
consistent with the fate of absorbed radioactivity from labeled free
propylene glycol and its metabolites. Five days after
administration of 5 g propylene glycol alginate (labeled in the
alginate moiety)/kg bw traces of radioactivity were still noted in
the rectum. It was concluded that released propylene glycol was
absorbed and metabolized by the usual pathways (to acetate, lactate
or glycogen) and had disappeared completely from the body after five
days. The alginate moiety and the unhydrolyzed propylene glycol
alginate were not absorbed from the gastrointestinal tract, but
excreted in the faeces (Sharratt & Dearn, 1972).
2.1.2 Biotransformation
No information available.
2.1.3 Effects on enzymes and other biochemical parameters
No information available.
2.2 Toxicological studies
2.2.1 Acute toxicity studies
The results of acute toxicity studies with propylene glycol
alginate are summarized in Table 1.
Table 1. Acute toxicity studies - propylene glycol alginate
Animal Route LD50 Reference
(mg/kg bw)
mouse oral 7 800 FDRL, 1976
rat oral 7 200 FDRL, 1976
hamster oral 7 000 FDRL, 1976
rabbit oral 7 600 FDRL, 1976
2.2.1.1 Rats
Groups of 60 rats were dosed with 5 g/kg bw propylene glycol
alginate by gavage or were fed a diet containing 50 to 70% propylene
glycol alginate for 24 hours. No adverse effects were observed.
Autopsy 14 days after treatment did not reveal compound-related
abnormalities (Woodard Res. Corp., 1972).
Rats given 10 g propylene glycol alginate/kg bw orally as a
suspension in corn oil showed a transient depression. No other
effects were noted (Newell & Maxwell, 1972).
2.2.1.2 Rabbits
Rabbits receiving an application of propylene glycol alginate
as an aqueous paste on abraded skin or receiving an ocular
application of dry powdered propylene glycol alginate did not reveal
signs of irritation (Woodard Res. Corp., 1972).
Rabbits injected intravenously, intraperitoneally,
intramuscularly or subcutaneously with 6.2, 12.5 or 25 mg propylene
glycol alginate/kg bw showed neither effects at the injection site
nor any systemic effects (Steiner & McNeely, 1951).
Rabbits injected subcutaneously or intramuscularly with up to
2 ml of a sterile aqueous 2% solution of propylene glycol alginate
did not show gross or histological abnormalities at the injection
site. Intraperitoneal and intravenous injections of similar amounts
did not produce abnormal systemic effects (Ouer et al., 1935).
2.2.2 Short-term toxicity studies
2.2.2.1 Rats
Two groups of 6 female rats received a diet containing 21.5%
propylene glycol alginate and 21.5% glucose or a normal diet
containing 21.5% glucose for 4 weeks. After 4 weeks of treatment 2
animals/group were killed and the remaining 4 animals/group received
a normal diet for an additional 4 weeks. Thereafter the original
control group received a diet containing 21.5% propylene glycol
alginate and the original test group received a control diet for 2
weeks. The test group showed slight growth retardation but
appearance and behaviour were normal. Faeces of the test group were
slimy. Histopathogy of liver, kidneys and intestine of the 2
animals/group that were killed after the initial 4 weeks treatment
time did not reveal abnormalities (MRCL, 1951).
Fifteen male rats received 5% (w/w) propylene glycol alginate
in the diet for 30 days. No diarrhoea was seen and bowel habit was
normal. Urinalysis did not reveal abnormalities. All rats showed
distension of the caecum, 5 rats showed distension of a portion of
the ileum. Twelve rats showed distension of the colon to some
degree, with soft contents. Soft ill-formed faecal pellets were
seen in 10 rats. No further macroscopic changes were seen.
Histopathology was not carried out (Anderson et al., 1991).
2.2.2.2 Guinea-pigs
Four groups of 3 guinea-pigs received 0, 5, 10 or 15% propylene
glycol alginate in their diet for 26 weeks. Body weight gain was
reduced in test groups but mean food intake was similar to controls.
Histopathology of various organs revealed no significant lesions
(Nilson & Wagner, 1951).
2.2.2.3 Cats
Eight experimental cats and one control cat were fed 0, 5, 10
or 15% propylene glycol alginate in a diet of dog food and canned
salmon daily for 88-111 days. Test animals had difficulties in
swallowing and eating because of the physical texture of the diet.
The animals could not eat more than 100 g dog food and 30 g canned
salmon/day and thus lost weight. At dietary levels of 10 and 15%
the cats showed frequent soft stools. Macroscopy and microscopy did
not reveal abnormalities (no details) (Nilson and Wagner, 1951).
2.2.2.4 Chickens
4 Groups of 13-day old chickens (number/group unknown) received
0, 5, 10 or 15% propylene glycol alginate in their diet for 3-7
weeks. At all dose levels growth rate was reduced due to
difficulties with the diet. Histopathology showed slight transient
tissue changes in controls as well as test animals (no details)
(Nilson & Wagner, 1951).
2.2.2.5 Dogs
Three groups of 3 male and 3 female Beagle dogs received a diet
containing 0, 5 or 15% propylene glycol alginate for one year.
Stool conditions were variable at the 15% dietary level. Weight
gain and food consumption were normal. No effects on haematological
(no details) parameters or serum urea nitrogen, serum alkaline
phosphatase, blood glucose or urinalysis (no details) were seen.
Organ weights (10) were comparable to controls. Histopathology
(21 tissues) did not reveal compound-related changes (Woodard,
1959).
2.2.3 Long-term toxicity/carcinogenicity studies
2.2.3.1 Mice
Four groups of 10 mice (bw 12-18 g) received 0, 5, 15 or 25%
propylene glycol alginate in their diet for 12 months. At week 39
one control mouse and one mouse of the group fed 15% in their diet
were killed. In the 25% group, increased mortality, a decreased
maximum body weight, decreased food intake and increased water
consumption were seen. At the 15% dose level a slightly decreased
maximum body weight and a slightly decreased food intake were seen.
The effects were probably due to increased water absorption of the
diet which caused enough bulk to limit food intake (Nilson & Wagner,
1951).
2.2.3.2 Rats
Four groups of 10 male and 10 female rats (age 4 weeks)
received during their life span 0, 5, 15 or 25% propylene glycol
alginate in their diet. At dose-levels of 15 and 25% in the diet
lifespan was slightly reduced and decreased food consumption was
seen. Death of rats in control as well as test groups was usually
due to myocardial fibrosis, pneumonia and the multiplicity of
cumulative processes associated with aging. There were no lesions
attributed to toxaemia or to local irritative intestinal effects.
The bulky diets caused loose and smeary faeces and weight gain was
reduced, probably due to inanition. Organ weights were not
determined. Histopathology of major tissues (liver, kidneys,
spleen, heart, brain, lung, stomach, small intestines, large
intestines, ovaries/testes) did not reveal abnormalities. A fifth
group received 15% propylene glycol alginate in a different basal
diet. This group showed an increased food and water consumption.
Faeces were normal in this group. The group was killed after 37
weeks (Nilson & Wagner, 1951).
Groups of 20 male and 20 female rats received 0% or 5%
propylene glycol alginate in their diet for 2 years as the parent
generation of a multigeneration study. Two male and two female
rats/group were killed after one year for histopathology. After 2
years survival of this F0 generation was 67% for males and 78% for
females in the control group and 56% for males and 58% for females
in the test group. Survival time was 761 days. No difference from
controls in general condition, general behaviour, skin, hair, eyes,
mean body weight, or haematology (4 males and 4 females/group) was
seen. Gross pathology and histopathology of 6 major organs did not
reveal treatment-related effects (Morgan, 1959).
2.2.4 Reproduction studies
2.2.4.1 Rats
Groups of 20 male and 20 female rats received 0 or 5% propylene
glycol alginate in their diet. After 5-6 months some animals were
mated to produce an F1 generation. 7 Males and 7 females were F1
controls and 10 males and 10 females the test group. The F1
generation was fed on similar diets and mated after 4 months to
produce the F2 generation. The F2 generation consisted of 9 male
and 10 female controls and 9 male and 10 female test animals and
were also kept on similar diets. F0 generation survived 761 days,
while F1 and F2 generation were killed after 202 and 212 days,
respectively.
No differences from controls were noted regarding mortality,
general condition, mean body weight, fertility, gestation data,
lactation and survival for the F1 and F2 generation. Haematology
was performed in the F2 generation only and did not show
abnormalities. Organ weights were not determined. Gross pathology
and histopathology of 6 major organs did not show abnormalities
(Morgan, 1959).
2.2.5 Special studies on genotoxicity
The results of genotoxicity studies are summarized in Table 1.
2.2.6 Special studies on teratogenicity
2.2.6.1 Mice
Groups of 22-32 pregnant albino CD-1 mice received daily from
day 6 to 15 of gestation 0, 8, 36, 170 or 780 mg propylene glycol
alginate/kg bw/dy by gavage as a suspension in corn oil. Up to 170
mg/kg bw/dy there was no effect on nidation or maternal or fetal
survival. The number of abnormalities seen in either soft or
skeletal tissues did not differ from the number occurring
spontaneously in controls. At 780 mg/kg bw/dy maternal toxicity
resulted in 7/32 deaths. Surviving dams and fetuses carried to term
appeared normal in all respects (FDRL, 1972).
2.2.6.2 Rats
Groups of 24 pregnant Wistar rats receved daily by gavage from
day 6 to 15 of gestation 0, 7, 33, 155 or 720 mg propylene glycol
alginate/kg bw/dy as a suspension in corn oil. On day 20 Caesarean
section was carried out and dams and fetuses were examined for
pathological and teratological effects. No compound-related effects
were observed (FDRL, 1972).
Table 1. Results of genotoxicity assays on propylene glycol alginate
Test system Test object Dose-levels Results References
Ames test Salmonella typhimurium up to 10 mg/plate neg1 Ishidate et al., 1984
(6 strains)
Ames test Salmonella typhimurium 5% w/v negative2 SRI, 1972
(2 strains)
Ames test Salmonella typhimurium up to 0.60% negative1 LBI, 1975
(3 strains)
Mitotic recomb. Saccharomyces cerevisiae D-3 up to 1% w/v negative2 SRI, 1972
Mitotic recomb. Saccharomyces cerevisiae D4 2.5, 5.0 and 10% negative1 LBI, 1975
Host-mediated assay Salmonella typhimurium oral doses to mice negative SRI, 1972
TA 1530 and G46 i.p. in for 1-5 days up to
mice 5 g/kg bw
Host-mediated assay Sacharomyces cerevisiae oral doses to mice negative SRI, 1972
D-3 i.p. in mice for 1-5 days up to
5 g/kg bw
Chromosomal aberration Chinese hamster fibroblasts up to 1.0 mg/ml negative2 Ishidate et al.,
assay (CHL cells) 1984; 1988
Chromosomal aberration human WI-38 cells up to 1.0 mg/ml negative2 SRI, 1972
assay
Table 1 (contd)
Test system Test object Dose-levels Results References
Micronucleus assay rat bone-marrow once orally 0.03, negative SRI, 1972
2.5, or 5.0 g/kg bw
or daily for 5 days
0.03, 2.5 or 5.0 g/kg bw
Dominant-lethal assay rats once orally 0.03, 2.5, negative SRI, 1972
or 5.0 g/kg bw or daily
for 5 days 0.03, 2.5 or
5.0 g/kg bw
1 Assay without and with metabolic activation.
2 Assay without metabolic activation.
2.2.6.3 Hamsters
Groups of 20 to 23 pregnant golden hamsters received daily by
gavage from day 6 to 10 of gestation 0, 7, 33, 150 or 700 mg
propylene glycol alginate/kg bw/dy as a suspension in corn oil. On
day 14 Caesarean section was carried out. There was no evidence of
maternal toxicity or effect on reproduction. Examinations of
fetuses did not reveal compound-related abnormalities (FDRL, 1974a).
2.2.6.4 Rabbits
Groups of 10 to 15 pregnant rabbits received daily by gavage
from day 6-18 of gestation 0, 8, 37, 173 or 800 mg propylene glycol
alginate/kg bw/dy as a suspension in corn oil. On day 29 Caesarean
section was carried out. No differences with respect to number of
corpora lutea, implantation sites, resorption sites, number of live
and dead fetuses or fetal weights were seen. Gross examination of
the fetuses did not reveal external congenital abnormalities.
Visceral and skeletal examination of fetuses from dosed does did not
show any differences compared to control fetuses (FDRL, 1974b).
2.2.7 Special studies on bacteriology
Two rats were fed control diet during 6 months, thereafter they
received 5% polyethylene glycol alginate in their diet for 3 weeks
followed by 2 weeks on control diet. Bacteriological examination of
the intestinal flora showed lower counts of lactobacilli and aerobes
but an increased count of coliforms compared to controls. The
anaerobic counts were comparable with those of controls (Woodard,
1959).
2.3 Observations in humans
Fifty individuals known to be allergic to numerous substances
were tested intradermally with various dilutions of propylene glycol
alginate. Fifty other individuals without an allergic history or
family history of allergy were used as controls. 11 Individuals
showed slight to moderate skin reactions (8 in test group, 3 in
control group). When five of those showing the greatest reactions
(all in test group) were fed propylene glycol alginate three showed
mild allergic reactions which were duplicated in repeated tests.
Three control individuals, who showed very slight skin reactions,
did not react to oral administration of propylene glycol alginate
(Ouer, 1949).
Five healthy male volunteers received 175 mg propylene glycol
alginate/kg bw/day orally for 7 days, followed by 200 mg/kg bw/dy
for a further 16 days. The daily doses were consumed in three
measured portions at intervals each day. The portions were prepared
by adding the weighed aliquots of propylene glycol alginate with
rapid stirring to 220 ml cold distilled water. The hydrocolloid was
then allowed to hydrate for 24 h to a thick but fluid gel to which
each volunteer added a pre-determined amount of orange juice prior
to consumption. The treatment period was preceeded by a 7-day
initial control period during which daily an amount of orange juice,
equal to that to be used later, was consumed. During the treatment
period enquiries were made with respect to apparent allergic
responses. At day 3 of the initial control period, on the last day
the of 23-day treatment period and on the last day of the 7-day
recovery period the following parameters were examined; fasting
blood glucose, plasma insulin, breath hydrogen concentrations,
haematological parameters (Hb, Hct, MCV, MCH, MCHC, Er, Leu, Diff,
platelets) and biochemical parameters (Na, Cl, K, CO2, urea, LDH
[lactate dehydrogenase], ASAT, bilirubin, alk. phosphatase,
phosphate, Ca, protein, albumin, creatinine, urate, lipids,
cholesterol, HDL cholesterol and triglycerides). Routine urinalysis
was carried out during the initial control week and during the third
week of treatment. Five-day faecal collections were made during
days 2-6 of the initial control period and during days 16-20 of the
treatment period. Faecal transit time, wet wt., dry wt., water
content, pH, occult blood, neutral sterols, fat, volatile fatty
acids and bile acids in faeces were determined. No allergic
reactions were observed. Propylene glycol alginate exerted no
significant effects on faecal parameters (pH, water content, wet and
dry wts.) Faecal transit time was constant in 3 volunteers,
increased in one and decreased in one. Faecal total and individual
volatile fatty acids and total and individual bile acids did not
show changes. Faecal total neutral sterols and cholesterol
decreased in each volunteer. Haematological, biochemical and
urinary parameters did not show significant changes (Anderson
et al., 1991).
3. COMMENTS
An in vitro study showed partial hydrolysis of propylene
glycol alginate in simulated intestinal juice (25% within 4 hours;
80% within 24 hours). Partial hydrolysis was also observed in an
in vivo mouse study. Absorption, distribution, and excretion
studies in mice showed that unhydrolysed propylene glycol alginate
and the alginate moiety were not absorbed. Released propylene
glycol was rapidly absorbed and metabolized to lactic and pyruvic
acids.
In various short- and long-term toxicity studies, 10% or higher
propylene glycol alginate in the diet caused reduced growth
accompanied by reduced food consumption and loose stools, the common
effects in animals fed high doses of bulking agents.
In a long-term toxicity study in mice (12 months) as well as in
long-term toxicity studies in rats (&gt 2 years) the NOEL was 5%.
There was no indication of a carcinogenic effect. Propylene glycol
alginate did not induce gene mutations in bacteria or in yeast cells
or chromosomal aberrations in mammalian cells in vitro or in vivo.
In addition, in a 2-generation reproduction study in rats, 5%
propylene glycol alginate in the diet did not cause any effects.
Teratogenicity studies in rats, mice, hamsters and rabbits did not
reveal any teratogenic activity of propylene glycol alginate at dose
levels of up to 800 mg/kg bw/day.
No adverse effects were observed in a recent 23-day study in
five human volunteers in which the substance was given orally at a
dose of 200 mg/kg bw/day.
4. EVALUATION
The Committee noted that similar effects - reduced growth, and
loose stool - have been observed in animal studies with other poorly
absorbed compounds (including modified cellulose, polyalcohols,
gums, modified starches and other alginates). The Committee
reiterated that the ADI for propylene glycol alginate is limited
only by the amount of propylene glycol that might be released.
Propylene glycol alginate containes up to 36% propylene glycol. On
the assumption that all of this amount is hydrolyzed, and taking
into account the ADI of 0-25 mg/kg by for propylene glycol, the
Committee allocated an ADI of 0-70 mg/kg bw (100/36 x 25) to
propylene glycol alginate.
The Committee was aware of new toxicological studies on
propylene glycol, but as the compound was not on the agenda, the
data were not reviewed. The Committee recommended that propylene
glycol be reviewed at a future meeting. Because the ADI for
propylene glycol alginate is based on the ADI for propylene glycol,
the Committee also recommended that the former substance be
reconsidered at the same meeting.
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